Type 1 diabetes mellitus (DMT1) and thyroid disease are the two most common endocrine disorders which often coexist in the same patient. Hashimoto's thyroiditis (HT), characterized with hypothyroidism and Graves' disease (GD), characterized by hypertiroidism are especially interesting due to the fact that they can interchange. Etiology of autoimmune thyroid disease is very complex and still not fully understood, therefore it is not surprising that we still do not have official nutrition recommendations. An observational study was conducted by using the anonymous questionnaire with the aim to assess dietary characteristics of DMT1 patients diagnosed with HT (DMT1+HT, N=23) in comparison to control (only DMT1, N=31). Only one patient had GD and 22 HT, 95.6 % are women, average age 27.5 ± 10.1 years. Obesity was detected only among DMT1+HT patients (10.5 %) which indicates potential role of slowed metabolism in hypothyroidism. No significant difference was found in dietary intake of six main food groups. However, DMT1+HT patients more often excluded milk and/or gluten from their diet as a result of self-education on the Internet. DMT1+HT patients eat more vegetables, especially green leafy vegetables which are important sources of goitrogens. They also tend to add salt to their food even before tying it more often (17.4 % in comparison to 16.1 %; p=0.008), and kitchen salt is important source of iodine (due to mandatory fortification). Professional education on dietary sources of iodine and goitrogens for people with thyroid disease is much needed in order to avoid search for alternative and often unverified information.